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Nuclear field theory (Bohr-Mottelson, II)

Nuclear field theory (Bohr-Mottelson, II)

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Nuclear field theory (Bohr-Mottelson, II)

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  1. Nuclear field theory (Bohr-Mottelson, II) Equivalent to RPA with dipole-dipole interaction

  2. Shifts of the lines are smaller than the uncertainty of the 2 qp energies.

  3. M1? E1

  4. B(E1)[arb. units] screening enhancement

  5. Transitional (X(5)) deformed

  6. 88 90

  7. Two-neutron transfer crossections

  8. Shape coexistence analysis by Zielinska et al. Collective degrees of freedom by IBA Good fit to energies, reasonable fit to E2 matrixelements Strong mixing

  9. Shell model

  10. 2 shell correction, zero pairing 1 3 4

  11. 1 and 2 merge into a state with 56 neutrons protons 42

  12. 3,4 3 1 4

  13. Two-state mixing Origin of mixing: pair scattering Size of the coupling: few 100 keV strong mixing E1 operator cannot move 2 particles

  14. Two-level mixing model strong branching very different M very different mixing

  15. i no mixing experiment 3:1 Zielinska et al 1.33:1

  16. nb pb b nb Pair scattering blocked: b partially blocked: pb not blocked: nb

  17. 2qp octupole collective octupole Collective dipole Sensitive to deformation yes no yes no no Relation between the E1 matrix elements B(E1,low):B(E1,8 MeV) experiment: 1:10 2qp- calculations: <1:1000 Coupling to other degrees of freedom Soft octupole mode

  18. Relation between M1 matrix elements M1 matrix elements are weakly deformation dependent

  19. 2 1 3 4

  20. Conclusions Origin of low-lying dipole strength? M1 or E1 by coupling to octupole Dipole branch to second 0+ new evidence for shape coexistence Occurrence for only few states is a consequence of Pauli Principle. Information about the microstructure. Derivation of mixing amplitudes problematic